The present invention generally relates to medical imaging procedures and to devices and pharmaceuticals capable of use therewith. The invention particularly relates to medical imaging techniques that utilize devices that exhibit a sufficient level of radioactivity for use as tracers in imaging a patient's gastrointestinal tract.
A variety of gastrointestinal motility disorders are known that can affect the movement of food as it passes through the human body from stomach through excretion. Dysmotility symptoms are generally inconsistent, and may include bloating, abdominal pain, nausea and vomiting, diarrhea, and/or constipation. A commonly used procedure in nuclear medicine is a gastric emptying study which measures the rate of emptying from the stomach into the small bowel (intestine). Using a standard physiologic meal (per the Society of Nuclear Medicine and Molecular Imaging guidelines) that is tagged with a radioactive tracer, an amount of material emptied from a subject's stomach over a period of time can be accurately determined to identify the presence of dumping syndrome, gastroparesis, and potentially other gastrointestinal disorders. The amount of radiation used is relatively small and allows for imaging at various times, typically up to four hours after consuming a meal. Imaging of the small and large bowels, however, requires different techniques.
A radiographic small bowel follow-through study can determine the passage of radio-opaque material (for example, materials comprising iodine or barium) through the small bowel and into the large bowel. This procedure requires serial imaging of the abdomen. Barium in particular tends to extend along the length of the small bowel as the barium mixes with food, rather than remaining intact as a point source. While this allows for good visualization of the anatomy of the small bowel, it may not accurately reflect the transit time of a food particle.
Transit through the small and large bowels has been performed using a resin compound (Toward a Relatively Inexpensive, Noninvasive, Accurate Test for Colonic Motility Disorders, Camilleri et al., In Gastroenterology 1992; 103:36-42) or activated charcoal labeled with an isotope and placed into a gelatin capsule (Colonic Transit Scintigraphy Labeled Activated Charcoal Compared with Ion Exchange Pellets, Burton et. al., Journal of Nuclear Medicine 1997; 38:1807-1810). Notably, the use of a resin compound requires an Investigational New Drug Application (IND) from the US Food and Drug Administration (FDA). In regards to the activated charcoal, the capsule may be subsequently enteric coated and then administered to the subject. Using a standard nuclear medicine gamma camera, this radioactive capsule can be followed through the small bowel. When the capsule reaches the large bowel the enteric coating and capsule dissolves, releasing the tracer into the colon. Measurement of the large bowel transit however is complicated by mixing of the tracer with the bowel contents. A percentage of tracer activity needs to be calculated in the ascending, transverse, descending and sigmoid colon. Furthermore, activated charcoal can be difficult to work with and the process of enteric coating can be demanding and time consuming. Additional assessment methods are thoroughly described in Methods for the Assessment of Small Bowel and Colonic Transit, Szarka et al., Semin. Nucl. Med. 2002 March; 42(2):113-123), the contents of which are incorporated herein by reference.
Measuring transit through the small and large bowels using a resin compound or activated charcoal requires the attention of a radiopharmacist and the radioactive tracers are conventionally produced locally for their own institutions. There are no known comparable products available from a commercial radiopharmacy.
In view of the above, it can be appreciated that there are certain problems, shortcomings or disadvantages associated with the prior art, and that it would be desirable if improved methods, devices, and pharmaceuticals were available for investigating gastrointestinal motility disorders, particularly if capable of remaining as a point source through the small and large bowels of a subject.